To use script with Compiz Fusion run it's [attachment:gajim2compiz.py modified version].

Disabling D-Bus-related capabilities of Gajim

You can turn off the ability to remote control Gajim. The setting you want is remote_control.

You can turn off the ability to use notification daemon (if there) cool notification popups. The setting you want is use_notif_daemon.

You can do this by setting you want to False in Preferences Window, Advanced Tab, Open Advanced Editor.
DBUS & KDE
KDE 3.4.3 doesn't appear to start a Dbus instance for the user by default. Adding the .bashrc lines from above to a ~/.kde/env/dbus.sh seems to the trick. This is under Gentoo, with /etc/init.d/dbus running.